You know that old saying, "you are what you eat?" While it might not be literally true, there is something to be said for the meaning behind it, which is that a healthy diet leads to a healthy body, and vice versa. Eat a bunch of junk, and you're probably going to feel like, well, junk. What you eat also affects the way you look on the outside, right down to your skin.

Carla Oates, aka The Beauty Chef, is a huge proponent of this concept, and has dedicated the last 17-odd years to proving it. As a young girl with skin allergies and eczema, she started making her own products using natural ingredients, and found that beautiful, healthy skin starts from the inside-out—and with the gut, specifically. This led Oates to create the first living skincare line, which incorporates the "good" types of bacteria our guts need. So needless to say, we trust her expertise.

The skincare guru is also an author, and her newest book, The Beauty Chef: Delicious Food for Radiant Skin, Gut Health and Wellbeing ($22, amazon.com), offers background on her research along with recipes that can enhance your own gut health, and ultimately, your skin.

We sat down with Oates to get her insight on the best foods for your skin, and she revealed to us the top 5 foods to get that lit-from-within type of glow. Read on to see what she had to say.

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1. Fermented Foods

"Lacto-fermented foods are rich in bio-available nutrients to feed the skin from within," says Oates. "The lacto-fermentation process helps predigest the food, so the nutrients are more available for the skin and body to use." These foods are also "great for improving digestion as they contain prebiotics and broad-spectrum probiotics." Oates suggests incorporating sauerkraut, kefir, and kimchi into your diet, as well as The Beauty Chef's GLOW Inner Beauty Powder, which contains 24 different skin-loving, fermented superfoods.

2. Dark Green Leafy Veggies

Think: kale, broccoli, and cabbage. According to Oates, "these cruciferous veggies are super rich in sulfur compounds that help detoxify the skin so it is lovely, clear and radiant."

3. Berries and Pomegranates

These two foods "are antioxidant rich, anti-inflammatory and are packed with nutrients to support collagen production and help protect the skin from UV stress and free radical damage."

4. Foods Rich in Omega 3s

Good examples of foods that contain omega 3s are flaxseeds, salmon, sardines, and chia, which "moisturize and smooth the skin from the inside and are also anti-inflammatory. Inflammation causes all sorts of skin problems including dryness and loss of skin tone as it breaks down collagen."

5. Foods Rich in Beta Carotene & Pro-Vitamin A

These types of foods, which include carrots, sweet potatoes, and dunaliealla salina (a microalgae found in GLOW Inner Beauty Powder) "help rejuvenate the skin and promote cell turnover," explains Oates. "Avocado is also bursting with skin boosting carotenoids and contains incredibly rejuvenating and moisturizing good fats that help make the carotenoids more available for the body to use because they are fat soluble."